| 801 | MAYO | MAYORQUIN, RAMON | | | SCAC4 |
| 802 | MAYS | MAYES FAMILY FARMS | | | SCAC4 |
| 803 | MAYT | MAY TRUCKING COMPANY | | | SCAC1 |
| 804 | MAYT | MAY TRUCKING CO | | | SCAC4 |
| 805 | MAYW | Maywood & Sugar Creek | 1/1980-7/2005 | | NAKINA |
| 806 | MAYW | Maywood & Sugar Creek | 1/80-7/2000 | | NRHS |
| 807 | MAYW | MAYWOOD & SUGAR CREEK | | | PWRC |
| 808 | MAYW | Maywood and Sugar Creek | | | RSRV |
| 809 | MAYW | MAYNARD | | | SCAC4 |
| 810 | MAZ | Mines Air Services Zambia Limited | IATA: Q3, IATA Prefix: 391, | Z | AVCODES |
| 811 | MAZ | Roan Air | IATA: Q3, IATA Prefix: 391, Name changed to Zambian Airways | Z | AVCODES |
| 812 | MAZ | Zambian Airways | IATA: Q3, Callsign: Mines, IATA Prefix: 391, ICAO designator changed to MBN. Formerly Roan Air | Z | AVCODES |
| 813 | MAZ | Mines Air Services Zambia | | | ICAO1 |
| 814 | MAZ | MAZ | | RU | TRAFFIC |
| 815 | MAZA | MAZZA VINEYARDS | | | SCAC4 |
| 816 | MAZD | MID AMERICAN SPECIALIZED TRUCKING L | | | SCAC4 |
| 817 | MAZDA | | | | TRAFFIC |
| 818 | MAZF | MADARIS TRANSPORTATION LLC (TRACK I | | | SCAC4 |
| 819 | MAZJ | MARVALBERT TRANSPORTATION INC | | | SCAC4 |
| 820 | MAZK | MACZUK INDUSTRIES INC | | | SCAC4 |
| 821 | MAZM | MARTINEZ, MARIO | | | SCAC4 |
| 822 | MAZN | MID AMERICAN SPECIALIZED TANKERS LL | | | SCAC4 |
| 823 | MAZO | MAZON PERALES, ALVARO | | | SCAC4 |
| 824 | MAZP | MAC TRANSPORT INC | | | SCAC4 |
| 825 | MAZQ | MY AMAZING INTERIORS INC | | | SCAC4 |
| 826 | MAZR | MAZER, BENJAMIN TRUCKING INC | | | SCAC4 |
| 827 | MAZT | MID-AMERICAN SPECIALIZED TRANSPORT | | | SCAC4 |
| 828 | MAZY | MAKYS TRANSPORT | | | SCAC4 |
| 829 | MAZZ | MAZER CHEMICAL | | | PWRC |
| 830 | MAZZI | Angelo Mazzi Costruzioni Generali e Ferroviarie SRL | | IT | VKM |
| 831 | MB | MNG Airlines Cargo | ICAO: MNB, Callsign: Black Sea, IATA Prefix: 716, Name changed to MNG Airlines. Designator MB reinstated by IATA | TR | AVCODES |
| 832 | MB | Execaire, Inc. | ICAO: EXA, Callsign: Canadian Execaire, Designator MB* recalled by IATA | CDN | AVCODES |
| 833 | MB | Malasyia Air Charter Company Ltd. | Callsign: Malaysia, | MAL | AVCODES |
| 834 | MB | Federal Express Corporation (Fedex) | ICAO: FDE, Callsign: Express, ICAO designator changed to FDX | USA | AVCODES |
| 835 | MB | MNG Airlines | ICAO: MNB, Callsign: Black Sea, IATA Prefix: 716, Name changed to MNG Airlines Cargo. Designator MB reinstated by IATA | TR | AVCODES |
| 836 | MB | Federal Express Corporation (Fedex) | ICAO: FDX, Callsign: Express, ICAO designator changed from FDE | USA | AVCODES |
| 837 | MB | M&B R.R., LLC | added 10/1997; 7/2000-7/2005 | | NAKINA |
| 838 | MB | Meridian & Bigbee R.R. Co. | 1/1975-1/1994; eliminated 10/1997 | | NAKINA |
| 839 | MB | Montpelier & Barre R.R. | 1/1975-1/1980; eliminated 1/1981 | | NAKINA |
| 840 | MB | Montpelier & Barre R.R. | 1/75-1/80; eliminated 1/81 | | NRHS |
| 841 | MB | Meridian & Bigbee R.R. Co. | 1/75-1/94; eliminated 10/97 | | NRHS |
| 842 | MB | M&B R.R., L.L.C. | added 10/97; 7/2000 | | NRHS |
| 843 | MB | *MONTPELIER & BARRE RAILROAD CO. | | | PWRC |
| 844 | MB | +M & B RAILROAD, LLC [MERIDIAN & BIGBEE RR CO.] | | | PWRC |
| 845 | MB | Meridian and Bigbee Railroad (M&B Railroad) | | | RSRV |
| 846 | MB | M & B RAILROAD LLC | | | SCAC4 |
| 847 | MB | Mercedes-Benz | | D | TRAFFIC |
| 848 | MB | Mansfelder Bergwegsbahn e.V | | DE | VKM |
| 849 | MBA | Automobilvertriebs Aktiengesellschaft | Callsign: Avag Air, Ceased operations. | A | AVCODES |
| 850 | MBA | Avag Air Fur Luftfahrt | Callsign: Avag Air, | A | AVCODES |
| 851 | MBA | Avag Air | | | ICAO1 |
| 852 | MBAB | MURRAY, BOB TRUCKING | | | SCAC4 |
| 853 | MBAD | MBA LOGISTICS LLC | | | SCAC4 |
| 854 | MBAE | MEDLINS BALE CARRIERS INC | | | SCAC4 |
| 855 | MBAG | MAYER BROTHERS APPLE PRODUCTS INC | | | SCAC4 |
| 856 | MBAH | M & B TANK LINES INC | | | SCAC4 |
| 857 | MBAK | MARKET BASKET | | | SCAC4 |
| 858 | MBAL | MERX GLOBAL LOGISTICS INC | | | SCAC4 |
| 859 | MBAN | MEBANE TRANSPORT COMPANY | | | SCAC4 |
| 860 | MBAP | MURRAY, BOB TRANSPORTATION LLC | | | SCAC4 |
| 861 | MBAS | MILLER, B A & SONS TRUCKING INC | | | SCAC4 |
| 862 | MBAU | MARTI INFRA AG | | CH | BIC |
| 863 | MBAU | MARTI INFRA AG | | | SCAC4 |
| 864 | MBAV | MT BALTIC ADONIA TANKSCIFFAHRTSGESE | | | SCAC4 |
| 865 | MBAW | MICHELE BOTTIGLIERI ARMATORE SPA | | | SCAC4 |
| 866 | MBB | Air Manas d/b/a Air Manas Ltd. Air Company | IATA: M2, Callsign: Air Manas, Founded in 2006. IATA designator changed to ZM | KS | AVCODES |
| 867 | MBB | Air Manas d/b/a Air Manas Ltd. Air Company | IATA: ZM, Callsign: Air Manas, Founded in 2006. Ceased operations. IATA designator changed to M2* | KS | AVCODES |
| 868 | MBB | Air Manas Air Company LLC | IATA: ZM, Callsign: Air Manas, IATA Prefix: 887, | KS | AVCODES |
| 869 | MBB | Air Manas | | | ICAO1 |
| 870 | MBB | Mansfelder Bergwerksbahn Verein e.V. | Benndorf | D | privat-bahn.de |
| 871 | MBB | Mecklenburgische Bäderbahn Molli | | DE | VKM |
| 872 | MBBA | MACK BROTHERS TRUCKING | | | SCAC4 |
| 873 | MBBB | Museumsbahn Bremerhaven-Bederkesa e. V. | | DE | VKM |
| 874 | MBBC | MACARBO INC | | | SCAC4 |
| 875 | MBBE | MYKLEBU | | | SCAC4 |
| 876 | MBBK | MAHONE BAY BOATWORKS | | | SCAC4 |
| 877 | MBBKB | Buckower Kleinbahn-Eisenbahnverein Märkische Schweiz e.V | | DE | VKM |
| 878 | MBBL | MAAN | | | SCAC4 |
| 879 | MBBT | MORRIS, B BROTHERS TRUCKING | | | SCAC4 |
| 880 | MBBU | MULTIBOXX LIMITED | | HK | BIC |
| 881 | MBBX | Tank Car Services, Inc. | added 1/1981; eliminated 1/1986 | | NAKINA |
| 882 | MBBX | Michael D. Boxberger | added 1/1980; 1/1980; eliminated 1/1981 | | NAKINA |
| 883 | MBBX | Michael D. Boxberger | added 1/80; 1/80; eliminated 1/81 | | NRHS |
| 884 | MBBX | Tank Car Services, Inc. | added 1/81; eliminated 1/86 | | NRHS |
| 885 | MBBX | TANK CAR SERVICES, INC. [MICHAEL D. BOXBERGER] | | | PWRC |
| 886 | MBBX | Tank Car Services Inc. | | | RSRV |
| 887 | MBC | Airjet Exploracao Aerea de Carga, Passageiros e Correios, Lda | Callsign: Mabeco, | ANG | AVCODES |
| 888 | MBC | Airjet Exploracao Aerea De Carga | | | ICAO1 |
| 889 | MBC | Transports de la région Morges–Biere–Cossonay | | CH | TRAFFIC |
| 890 | MBC | Transports de la région Morges-Bière-Cossonay | | CH | VKM |
| 891 | MBCB | MTI BUS COMPANY | | | SCAC4 |
| 892 | MBCC | MARBLE CLIFF OIL CO | | | SCAC4 |
| 893 | MBCE | MALLETTE BROTHERS CONSTRUCTION COMP | | | SCAC4 |
| 894 | MBCH | MAIBACH TRACTOR LLC | | | SCAC4 |
| 895 | MBCI | MISSOULA BOTTLING COMPANY INC | | | SCAC4 |
| 896 | MBCJ | MARTINEZ BRIONES, CLAUDIA JULIANA | | | SCAC4 |
| 897 | MBCK | M B TRUCKING INC | | | SCAC4 |
| 898 | MBCL | MAILBOAT COMPANY LTD, THE | | | SCAC4 |
| 899 | MBCO | MABCO TRANSIT INC | | | SCAC4 |
| 900 | MBCQ | M & B CARRIERS INC | | | SCAC4 |
